A seating platforms comprising a rigid frame embedded in elastic material

ABSTRACT

A seating platform has a frame of cold rolled blue steel surrounding it and a web of rubber spanning the area of the frame. The web has a tensile strength of at least 1.6 kg/mm2 and an elongation of at least 500%. The platform can be placed on a seat without any securing means although it is preferred to fit it in a rabbet.

United States Patent 1191 Steele et al.

[ SEATING PLATFORMS COMPRISING A RIGID FRAME EMBEDDED IN ELASTIC MATERIAL [75] Inventors: Ralph Steele; John Peter Goodier,

both of Johannesburg, South Africa [73] Assignee: Steele Brothers (Proprietary) Limited, Johannesburg, South Africa [22] Filed: June 21, I973 [21] Appl. No.: 372,291

[52] US. Cl. 428/33; 297/DIG. 1; 297/455; 297/452; 428/67; 428/81 [51] Int. Cl. B32b 3/02; B32b [5/06; A470 7/02 [58] Field of Search [61/44, 221, 149; 297/DIG. l, 452, 455

[56] References Cited UNITED STATES PATENTS 2,838,100 6/l958 Follows 1, 297/DlG. l

[111 3,895,141 1451 July 15,1975

2,892,489 6/l959 Hurley 297/010 1 2,901,028 8/1959 Bottlemiller..... 297/010. 1 2,946,374 7/1960 Dickey 297/010. 1 3,259,435 7/1966 Jordan, .lr. 297/455 3,262,136 7/1966 Sevcik........... 297/010. 1 3,736,022 5/1973 Radke 297/010. 1

Primary Examiner-Philip Dier Attorney, Agent, or FirmYoung & Thompson ABSTRACT 7 Claims, 3 Drawing Figures Iwr.

A SEATING PLATFORMS COMPRISING A RIGID FRAME EMBEDDED IN ELASTIC MATERIAL This invention relates to seating platforms for chairs, settees, and like articles of furniture. The term platform is here used as meaning a support for that part on which a person sits as well as the back rest, usually known as a squab.

Platforms made of rubber and other elastomers are well known and are used particularly in the motor industry. These platforms are however usually composed of sheets secured to frames by various types of attaching hooks or extensions on the platform. Another lesser known platform includes a metal peripheral frame over which a textile material which may be elastic is stretched, with at least the underside of the assembly covered with a layer of rubber or other elastomer. The sides of the frame are sometimes slightly flexible in the plane of the platform to contribute towards the resil ience of the platform. This type of platform is usually affixed to a chair frame by means of fastening means located at its corners. Such platforms are not only easily secured to chair frames, but are also relatively easily manufactured.

[t is an object of this invention to provide a platform of the type comprising a frame surrounding a web as described above which eliminates the textile web or the requirement that the frame sides be flexible to contribute towards the resilience of the platform.

A further object is to provide a platform that does not need to be fixed to the frame ofa chair but may merely be positioned in a suitable receiving zone to perform its supporting function with no further attachment.

According to the invention a platform composed of a closed metal frame surrounding the area of the plat form and a web spanning that area is characterised in that the web is made from an elastomer the composition and thickness of which are chosen so that the web will flex but not yield under the maximum load it is intended to carry, and the metal used for and the dimensions of the frame are selected to ensure that the frame does not permanently deform under forces exerted on it by the web.

Further according to the invention the frame is made from a metal having a tensile strength of at least I50 kg/mm and preferably in the range l50 to 170 kg/mm An example of a suitable metal is cold rolled grey-blue steel. The frame is preferably made by bending a metal band into the desired closed figure and joining the ends of the band.

The invention also provides a method of making a platform including the steps of sandwiching a metal frame between layers of an elastomer, at least one of the layers covering the area defined by the frame, and bonding the layers together around the frame.

The invention is now discussed further with reference by way of example to the accompanying drawings in which:

FIG. 1 is a sectional view of a platform according to the invention,

HO. 2 is a plan view of a frame for a platform as shown in FIG. I, and

FIG. 3 is a perspective view of a chair frame with a platform as shown in FIG. 1 about to be located in position on the frame.

Referring to FIG. 1 of the drawings, a platform 2 according to the invention comprises a metal frame 6 embedded in a rubber web 4. The frame 6 is made from a band of cold rolled grey-blue steel having a tensile strength of between 150 and l7O kg/mm. The band is bent into the form of a square (or alternatively any other suitable closed figure) with rounded corners and the ends are welded together at 10 to complete the frame 6 as shown in FIG. 2.

The width, w, and the thickness, 1, of the band 6 are 10 mm and 1.7 mm respectively.

A typical rubber suitable for use for the web 4 has a tensile strength of at least 1.60 kg/mm and an elongation of at least 500%.

In one case the rubber used for the web 4 is processed as follows, all formulations being given as parts by weight.

parts of, a smoked sheet no. 1 Natural Grade rubber are masticated in an open mill for 30 minutes. The rubber is then sheeted off and allowed to settle until the following day. On the following day the rubber is placed into the mill and masticated for about 5 minutes. Then 5.00 parts of activated zinc oxide, L00 parts of stearic acid, and 1.20 parts of a protective agent which protects the rubber against ozone attack and prevents blooming are mixed for approximately 3 minutes. Following this 50.00 parts of a reinforcing silica powder used as a filler and having very good tensile and elongation properties, are mixed, with gradual addition of 5 parts of batching oil.

Following this 1.25 parts of an accelerator curing agent and 0.30 parts of a booster accelerator curing agent are added and blended for about 2 minutes. Finally 220 parts of sulphur are added and the mixture given a good dispersion. The mixture is then sheeted off and cooled in water. The sheet is then calendered at between 49 to 60C, and rolled on to a table to obtain a sheet 55mm wide and 2.l to 2.2 mm thick. The rubber in sheet form is now ready for use.

Using this rubber, and the frame 6 described above, the platform 2 is manufactured as follows:

A 0.4 mm X 5 mm strip of rubber prepared as described above, is placed around the edge of a mould. The steel frame 6 is then placed on the strip and finally a sheet 2.1 mm thick of the rubber is placed on top of the frame 6.

The sheet covers the entire area defined by the frame, thus forming the web 4. The mould is closed and pressed. The temperature of the mould is 655C, the closed time is 6 minutes and the pressure is 100 kg per square cm. The mould is opened and the composite structure allowed to cool. The platform 2 is completed by trimming the flash around the edges with a suitable cutting device, such as curved scissors.

FIG. 3 shows how a platform 2 as described above is fitted on the frame of a chair 8.

The frame of the chair 8 is provided with rabbet 12 which support the platform 2. There is no need to screw or otherwise to secure the platform 2 to the frame 8.

When someone sits on a chair which includes such a platform 2, a comfortable resilience is provided by the rubber web 4, and the steel frame 6 remains rigid. Thus the platform 2 remains in place on the rabbet l2 supporting it.

By choosing a suitable elastomer for the web 4 and a suitable metal for the frame 6, a platform 2 having the desired resilient characteristics is obtained.

We claim:

1. A seat capable of resiliently supporting the weight of a person, including a supporting frame surrounding a seating aperture and a platform covering the seating aperture, the platform being of an elastic sheet material and having a closed metal frame embedded in the elastic material substantially along the borders of the platform and wherein the platform lies loosely on the supporting frame and at least part of the metal frame is supported by the supporting frame.

2. A seat as claimed in claim 1, wherein the closed metal frame is of a metal having a tensile strength of at least 150 kglmm 3. A seat as claimed in claim 2, wherein the tensile strength of the metal is between 150 and I kglmm 4. A seat as claimed in claim 3, wherein the metal is cold rolled grey-blue steel.

5. A seat as claimed in claim 1, wherein the elastic material is an elastomer having a tensile strength of at least 1.6 kglmm 6. A seat as claimed in claim 1, wherein the elastic material is an elastomer having an elongation of at least 500%.

7. A seat as claimed in claim 1, wherein the suppporting frame has upwardly opening rabbets bordering said aperture, the edges of said platform resting in said rabbets.

* i a: :k 

1. A SEAT CAPABLE OF RESILIENTLY SUPPORTING THE WEIGHT OF A PERSON, INCLUDING A SUPPORTING FRAME SURROUNDING A SEATING APERTURE AND A PLATFORM COVERING THE SEATING APERTURE, THE PLATFORM BEING OF AN ELASTIC SHEET MATERIAL AND HAVING A CLOSED METAL FRAME EMBEDDED IN THE ELASTIC MATERIAL SUBSTANTIALLY ALONG THE BORDERS OF THE PLATFORM AND WHEREIN THE PLATFORM LOOSELY ON THE SUPPORTING FRAME AND AT LEAST PART OF THE METAL FRAME IS SUPPORTED BY THE SUPPORTING FRAME.
 2. A seat as claimed in claim 1, wherein the closed metal frame is of a metal having a tensile strength of at least 150 kg/mm2.
 3. A seat as claimed in claim 2, wherein the tensile strength of the metal is between 150 and 170 kg/mm2.
 4. A seat as claimed in claim 3, wherein the metal is cold rolled grey-blue steel.
 5. A seat as claimed in claim 1, wherein the elastic material is an elastomer having a tensile strength of at least 1.6 kg/mm2.
 6. A seat as claimed in claim 1, wherein the elastic material is an elastomer having an elongation of at least 500%.
 7. A seat as claimed in claim 1, wherein the suppporting frame has upwardly opening rabbets bordering said aperture, the edges of said platform resting in said rabbets. 